This invention relates to electrical control apparatus and, more particularly, to electrical control apparatus including an optical impulse generator and a light responsive circuit for controlling an electrical load.
As is appreciated by those skilled in the art, it is often desirable to transfer information or control signals by light energy rather than by electrical energy, especially when the constraints of the operating environment preclude using conventional electrical information transfer systems. For example, high voltage switching circuits use optical fibers and light transmission techniques to electrically isolate a low power switching circuit from a high voltage load. The same electrical isolation property of fiber optic systems makes them valuable in patient monitoring instruments for preventing a patient from being inadvertently connected to a source of electrical power. The optical fibers' light weight and their immunity to electrical interference and nuclear radiation are properties which make fiber optics systems especially useful in weapons systems and aircraft control systems where high reliability and survivability are critical. Light transmission or fiber optics systems are also ideal for use in explosive and inflammable environments in order to avoid the hazards associated with conventional electrical circuits.
Lighting control systems are another important application of fiber optics. In large office buildings, tons of copper wire are typically used to interconnect lighting loads with their respective control switches. Copper is an expensive and critical material and should be conserved whenever possible. One step toward conserving the use of copper involves substituting a fiber optic control system that uses light-weight, inexpensive optical fibers instead of copper control wiring.
Fiber optic systems transfer control signals and transmit other information by passing light, usually in impulse form, through optical fibers from one point to another. The light impulse is generated by an optical impulse generator. At the receiving end of the optical fibers, circuitry responsive to the light pulse transforms the pulse into electrical energy for controlling other electrical or mechanical devices. No electrical current is transmitted along the fibers. In some applications, however, optical fibers may not be required, for example where the light impulses from the optical impulse generator can be provided directly to the light responsive circuitry, or by an arrangement or combination of lenses, prisms and mirrors.
Optical impulse generators typically are made up of two cooperative assemblies or circuits. The first is a device for producing an impulse of electrical energy, or an electrical impulse generator. The electrical impulse generated thereby is conveyed to the second assembly which includes a light-emitting device for transforming the electrical energy into light energy.
An example of one type of electrical impulse generator is a mechanical apparatus having a spring loaded transmitter for converting an actuating motion into a mechanical impulse. The mechanical impulse is applied to a piezoelectric crystal which transforms the mechanical pressure into an electrical impulse at an output. The electrical impulse which is produced by this method is typically one having high voltage and low current characteristics. The output obtained is therefore suitable for exciting a high voltage low current light emitter, most commonly a neon bulb. A piezoelectric crystal is generally unsatisfactory for most electrical impulse generator applications, however, because the voltage generated by the crystal cannot be varied at the output. As a consequence, the variety of light-emitting devices which can be used with a generator equipped with a piezoelectric crystal is severely limited and, in most practical cases, such a generator is suitable for use only with neon bulb light emitters. Such generators typically cannot be used with improved solid state semiconductor light emitters which possess higher coupling efficiences than neon bulbs. Furthermore, such generators have limited or even no capacity to drive multiple light-emitting devices. Additionally, such generators typically operate as one pulse-on, one pulse-off switches which give no indication of the present state of a system, especially of the state in which the load is set. If the switch is in one compartment, and the load is located in a remote compartment out of view of the operator, the operator will have no indication of the state to which he has set the load when he depresses the switch.
Therefore, it is an object of this invention to provide a light tranmission load control system which controls and indicates the state in which the load is set.
Another object of this invention is to provide a light transmission load control system including an improved electrical impulse generator adaptable for use in combination with a light emitter which provides optical impulses to control an optically responsive load controller.
A further object of this invention is to provide such an improved electrical impulse generator having a multi-position switch capable of generating multiple electrical impulses, and indicating the impulse generated on the basis of switch position.
A further object of this invention is to provide such an improved electrical impulse generator having an electrical output that is adjustable so that it is usable with various light emitters having desirable coupling efficiences.
Still another object of this invention is to provide such an improved electrical impulse generator having only one moving part.